Glass transition in processing and stability of food

Many dry food products are predominantly in an amorphous glassy state where the amorphous solid has the property of a solution. Molecules are fixed an d the molecular mobility is halted at this state. If this solid solution is heated, abrupt changes in thermo-physical properties occur and the solid s tate is converted to a "rubbery" state. The temperature at which this chang e occurs is called the glass transition temperature (T-g). At this temperat ure and above, molecular mobility is regained, accelerating various physica l and chemical chang;es in food which may be detrimental to quality. This p aper reviews the importance of glass transition temperature in dried foods, frozen foods, bakery and confectionery products, and in drying and extrusi on cooking processes.